1. Field of the Invention
The present invention relates to a light scanning type confocal microscope in which excitation light is applied to a sample while being scanned and fluorescence exiting from the sample is detected.
2. Description of the Related Art
In recent years, along with development in fluorescence reagents, the functions of a laser scanning type confocal microscope (CLSM) increase. In addition to conventional fluorescence detection using a filter, a scheme of spectrally detecting fluorescence generated by a sample has become available. With fluorescence spectral detection, the fluorescence spectrum unique to each reagent can be quantitatively analyzed in more detail. Also, fluorescence observation is performed with a sample obtained by combining fluorescence reagents having large cross talk in their wavelength characteristics. A demand has arisen for observation of the individual fluorescence separately.
U.S. patent application Publication No. 2002/0020819A1 discloses an apparatus that spectrally detects fluorescence that is generated by a sample excited by a laser beam. More specifically, this apparatus spectrally separates fluorescence generated from the sample with a dispersion element of a diffraction grating, and detects the spectral fluorescence by a multi-channel detector. The multi-channel detector comprises detection channels, which are separated physically. The dispersed fluorescence is spatially distributed into the individual channels, and each distributed fluorescence is separated in its wavelength region and detected. Therefore, each channel has a minimal wavelength band width. The spectral profile of the fluorescence is acquired by electrically identifying the detection position of each channel or moving the detection position.
U.S. Pat. No. 6,809,815 discloses another apparatus that spectrally detects fluorescence. According to this apparatus, among fluorescence that is dispersed by a dispersion element comprising a prism, the fluorescence in a wavelength band that depends on the aperture width of a slit is detected. When at least one optical component on the optical path is rotated or slid, (the central wavelength of) the wavelength band is changed. Thus, a spectral profile is acquired.
U.S. Pat. No. 5,192,980 discloses still another apparatus that spectrally detects fluorescence. According to this apparatus, the fluorescence is dispersed by a dispersion element comprising a diffraction grating. A pinhole formed in front of a detector obtains a confocal effect and selects the wavelength. When the dispersion element is rotated in the same manner as in U.S. Pat. No. 6,809,815, the wavelength is selected by the pinhole within a desired region. A very narrow wavelength width is selected in accordance with the size of the pinhole, and highly accurate spectral detection is performed.